When talking about treat value, make sure to consider the value from the dog's point of view. It doesn't matter if you think a particular treat should be the most valuable if your dog prefers a different one. Usually we can tell by a dogs reaction to different treats in the same situation which they prefer more. It is a good idea to create a rough ranking of treats so that you can choose the treat that best suits the situation.
Generally we can classify treats into Low, Medium and High value treats. Low value treats are those that your dog will accept but aren't anything very special. Usually kibble falls into this category. High value treats are those treats that your dog gets excited to see, and will do almost anything for. Treats in this category tend to be meaty and smelly.
Here is an example of treat values for two different dogs illustrating how there can be some general trends but also some variation between individuals.